Surface Layer Effects Synergism with Electrolytes for Li Nucleation and Growth

Abstract

Li metal has been considered the “holy grail” anode materials. Li metal has the most negative potential with an extremely high theoretical specific capacity of 3860 mA h g−1.[1] It is, however, plagued with multiple challenges which need solutions before the realization of this material. Li metal has two main failure mechanisms, one is the random growth of detrimental dendrites, which can lead to rapid thermal runoff, i.e. Galaxy Note 7.[2] The other issue that arises upon cycling is pulverization of lithium metal through none uniform plating, leading to an increase in solid electrolyte formation(SEI) and thereby the increase in voltage polarization within the cell.[3] Both Li failure mechanisms are rooted in the uneven distribution of SEI layers whose properties vary depending on the location of SEI formed.[4] The initial surface chemistry on Li metal influences SEI formation in the very beginning. In this work, electrochemical deposition of Li metal on different substrates with bare oxides has been performed to understand the nucleation and growth of Li crystals. Electrolyte and surface modification give rise to differing SEI properties/composition which leads to improved Li deposition morphology. The fundamental mechanisms that dictates the smooth Li deposition will be discussed.